1. Field of the Invention
The present invention relates to an evaporator for evaporating a liquid raw material to thereby generate a start gas used in a layer-formation apparatus such as a chemical vapor deposition (CVD) apparatus, a metal organic chemical vapor deposition (MOCVD) apparatus, an atomic layer deposition (ALD) apparatus or the like.
2. Description of the Related Art
For example, JP2005-039120 A discloses a prior art evaporator which generates a start gas used to form a metal oxide layer on a semiconductor wafer such as a silicon wafer in a layer-formation apparatus.
The evaporator includes an evaporating chamber defined therein, and an atomizer for atomizing a liquid raw material containing a suitable solvent component and an organic metal component with a carrier gas to thereby produce a plurality of fine liquid-phase particles or mists. The mists are introduced into the evaporating chamber, and then are thermally evaporated to thereby generate the start gas, which is fed from the evaporating chamber to the layer-formation apparatus through a start-gas supply passage formed in the evaporator.
When the mists cannot be completely evaporated in the evaporating chamber, a part of the excess mists is entrained with the start gas fed to the layer-formation apparatus, and the entrained mists cause mist defects on a layer to be formed on the semiconductor wafer in the layer-formation apparatus. Thus, the entrainment of the mists with the start gas mist must be prevented before the layer can be free from the mist defects.